Added the lowercase and uppercase mutations to the mutate filter.
Added the lowercase and uppercase mutations to the mutate filter.

A fairly simple feature addition, each mutation will check to see
if the input is a string before calling either .upcase! or .downcase!

tinglinux/logstash-kafka,joekiller/logstash-kafka,opentable/logstash-kafka,joekiller/logstash-kafka,opentable/logstash-kafka,Aloomaio/logstash-kafka,tinglinux/logstash-kafka,Aloomaio/logstash-kafka